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FIRE Number Calculator

Calculate your FIRE (Financial Independence, Retire Early) number — the portfolio size at which a safe withdrawal of returns covers your annual expenses indefinitely.

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A FIRE (Financial Independence, Retire Early) number is the portfolio size at which the safe withdrawal of investment returns covers your annual expenses indefinitely. It is the headline target the FIRE community plans against — derived from the Trinity Study and the 4% rule.

Enter your annual expenses (what you spend in a typical year, including housing, food, healthcare, and a realistic discretionary buffer). The default safe withdrawal rate of 4% is the standard starting point; lower it to 3% for a more conservative target or raise it to 5% if you plan to have flexible spending. Optionally enter your current invested savings, monthly contribution, and expected return to see your progress and projected years to financial independence.

Examples

$40,000/year lifestyle, 4% SWR

A household spending $40,000/year hits FIRE at $1,000,000 (40,000 / 0.04). Conservative target (3%): $1,333,333. Aggressive target (5%): $800,000.

$60,000/year lifestyle, with current savings

Annual expenses $60,000, SWR 4% → FIRE number $1,500,000. With $300,000 already invested and $2,500/month contributions at 7% real return, projected years to FI ≈ 18.

Coast FIRE check

If your current savings × (1 + r)^t equals your FIRE number for some realistic t (e.g. 25 years to a normal retirement age), you have hit Coast FIRE — you can stop new contributions and just let compounding finish the job.

Frequently Asked Questions

Where does the 4% rule come from?
The Trinity Study (1998) and earlier work by William Bengen (1994) tested historical US stock/bond portfolios over 30-year retirements and found that withdrawing 4% of the initial portfolio (adjusted for inflation each year) had a high probability of not exhausting the principal. It is a rule of thumb, not a guarantee.
Should I use 3%, 4%, or 5%?
Use 4% if you plan a 30-year retirement, are flexible about spending in down years, and are comfortable with a small chance of running out. Use 3–3.5% if your retirement horizon is 40+ years (early retirement) or you want a higher safety margin. Use 5% only if you have flexible income (part-time work, rental income, Social Security) that can cover shortfalls.
Does the FIRE number include taxes?
No — it is portfolio size, not after-tax spending power. Build your tax bill into "annual expenses." If you withdraw $40,000/year and pay $5,000 in taxes, your effective annual expenses are $45,000 and your FIRE number is $1.125M, not $1M.
What about inflation?
Use real (inflation-adjusted) figures throughout: today's dollar expenses and a real return assumption (~7% for US equities). The 4% rule already accounts for inflation by adjusting the annual withdrawal each year. Mixing nominal returns with real expenses will overstate your progress.
Is FIRE number the same as Coast FIRE?
No. FIRE number is the target portfolio size at which you can stop working entirely. Coast FIRE is the (smaller) amount you need today such that, with no more contributions, compound growth alone reaches your FIRE number by traditional retirement age. Coast FIRE is a milestone on the way to full FIRE.
Why does Years to FI sometimes show "unreachable"?
If your monthly contribution and expected return are both zero, you cannot reach a non-zero target. If contributions are very small relative to the gap, the projection caps at 100 years.

References

  1. Bengen, W. P. (1994). "Determining Withdrawal Rates Using Historical Data." Journal of Financial Planning. — Original 4% rule paper
  2. Trinity Study (Cooley, Hubbard, Walz, 1998) — AAII Journal — extension of Bengen using a wider asset mix
  3. r/financialindependence community wiki — https://www.reddit.com/r/financialindependence/wiki/
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Coast FIRE Calculator
4% Rule Retirement Calculator
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Quick Tips

  • •Track expenses for at least 12 months before fixing your annual-expenses number. Annualised one-month spending almost always undercounts.
  • •Add a 10–15% buffer to whatever you tracked — irregular costs (replacement appliances, car repairs, medical, travel) are where FIRE plans fail.
  • •Use real (inflation-adjusted) returns for the projection. The historical US equity average is about 7% real, not the 10% nominal you see quoted.
  • •Re-run this calculator when your expenses change. Lifestyle inflation moves the goalpost; the FIRE number scales linearly with annual spend.
  • •For early retirement (40+ year horizon) lean toward 3.25–3.5% SWR. The 4% rule was studied for a 30-year retirement.

A FIRE (Financial Independence, Retire Early) number is the portfolio size at which the safe withdrawal of investment returns covers your annual expenses indefinitely. It is the headline target the FIRE community plans against — derived from the Trinity Study and the 4% rule.

How to Use This Calculator

Enter your annual expenses (what you spend in a typical year, including housing, food, healthcare, and a realistic discretionary buffer). The default safe withdrawal rate of 4% is the standard starting point; lower it to 3% for a more conservative target or raise it to 5% if you plan to have flexible spending. Optionally enter your current invested savings, monthly contribution, and expected return to see your progress and projected years to financial independence.

Understanding the Formula

FIRE number = Annual expenses / Safe withdrawal rate. With the standard 4% SWR, this simplifies to 25 × annual expenses. At 3% SWR it becomes 33.3 × expenses; at 5% SWR it is 20 × expenses. Years to FI is solved numerically from the annuity future-value formula: target = PV(1+r)^t + 12 × PMT × [((1+r)^t − 1) / r]. This is a planning approximation — the solver compounds annually with year-end contributions, so actual outcomes depend on monthly cash-flow timing and real-world return variance.

Examples

$40,000/year lifestyle, 4% SWR

A household spending $40,000/year hits FIRE at $1,000,000 (40,000 / 0.04). Conservative target (3%): $1,333,333. Aggressive target (5%): $800,000.

$60,000/year lifestyle, with current savings

Annual expenses $60,000, SWR 4% → FIRE number $1,500,000. With $300,000 already invested and $2,500/month contributions at 7% real return, projected years to FI ≈ 18.

Coast FIRE check

If your current savings × (1 + r)^t equals your FIRE number for some realistic t (e.g. 25 years to a normal retirement age), you have hit Coast FIRE — you can stop new contributions and just let compounding finish the job.

Frequently Asked Questions

Where does the 4% rule come from?

The Trinity Study (1998) and earlier work by William Bengen (1994) tested historical US stock/bond portfolios over 30-year retirements and found that withdrawing 4% of the initial portfolio (adjusted for inflation each year) had a high probability of not exhausting the principal. It is a rule of thumb, not a guarantee.

Should I use 3%, 4%, or 5%?

Use 4% if you plan a 30-year retirement, are flexible about spending in down years, and are comfortable with a small chance of running out. Use 3–3.5% if your retirement horizon is 40+ years (early retirement) or you want a higher safety margin. Use 5% only if you have flexible income (part-time work, rental income, Social Security) that can cover shortfalls.

Does the FIRE number include taxes?

No — it is portfolio size, not after-tax spending power. Build your tax bill into "annual expenses." If you withdraw $40,000/year and pay $5,000 in taxes, your effective annual expenses are $45,000 and your FIRE number is $1.125M, not $1M.

What about inflation?

Use real (inflation-adjusted) figures throughout: today's dollar expenses and a real return assumption (~7% for US equities). The 4% rule already accounts for inflation by adjusting the annual withdrawal each year. Mixing nominal returns with real expenses will overstate your progress.

Is FIRE number the same as Coast FIRE?

No. FIRE number is the target portfolio size at which you can stop working entirely. Coast FIRE is the (smaller) amount you need today such that, with no more contributions, compound growth alone reaches your FIRE number by traditional retirement age. Coast FIRE is a milestone on the way to full FIRE.

Why does Years to FI sometimes show "unreachable"?

If your monthly contribution and expected return are both zero, you cannot reach a non-zero target. If contributions are very small relative to the gap, the projection caps at 100 years.

Assumptions & Limitations

  • Returns are constant year over year. Real markets are sequential and volatile; sequence-of-returns risk in the first 5–10 years of retirement is the single biggest threat to a 4% withdrawal plan.
  • Annual expenses stay flat in real (inflation-adjusted) terms. Use today's dollars throughout — do not inflate the expense number, and use real (post-inflation) returns (~7% historical equity average).
  • Expenses already include healthcare, taxes on withdrawals, and a buffer for irregular costs. The most common error in FIRE planning is omitting these.
  • No part-time / barista income, no Social Security, no inheritance, no rental income. Add those by reducing the "annual expenses" input by their contribution.
  • The 4% rule comes from a 30-year US retirement window (Trinity Study). Earlier retirement (40+ year horizon) typically warrants 3–3.5%.

References

  1. Bengen, W. P. (1994). "Determining Withdrawal Rates Using Historical Data." Journal of Financial Planning. — Original 4% rule paper
  2. Trinity Study (Cooley, Hubbard, Walz, 1998) — AAII Journal — extension of Bengen using a wider asset mix
  3. r/financialindependence community wiki — https://www.reddit.com/r/financialindependence/wiki/